Solution polymerization processes are typically carried out at temperatures above the melting point of the ethylene interpolymer being synthesized. In a typical solution polymerization process, catalyst components, solvent, monomers and hydrogen are fed under pressure to one or more reactors.
For ethylene homo polymerization, or ethylene copolymerization, reactor temperatures can range from about 80° C. to about 300° C. while pressures generally range from about 3 MPag to about 45 MPag and the ethylene interpolymer produced is dissolved in a solvent. The residence time of the solvent in the reactor is relatively short, for example, from about 1 second to about 20 minutes. The solution process can be operated under a wide range of process conditions that allow the production of a wide variety of ethylene interpolymers. Post reactor, the polymerization reaction is quenched to prevent further polymerization, by adding a catalyst deactivator, and passivated, by adding an acid scavenger. Once passivated, the polymer solution is forwarded to a polymer recovery operation where the ethylene interpolymer product is separated from process solvent, unreacted residual ethylene and unreacted optional α-olefin(s).
The polymer industry is in constant need of improved ethylene interpolymer products in flexible film applications, non-limiting examples include food packaging, shrink and stretch films. The inventive ethylene interpolymer products disclosed herein have performance attributes that are advantageous in many film applications. Elaborating, relative to competitive polyethylenes of similar density and melt index, some embodiments of the disclosed ethylene interpolymers after converting into films have one or more of: higher stiffness (e.g. tensile and/or flex modulus); higher toughness properties (e.g. impact and puncture); higher heat deflection temperatures; higher Vicat softening point; improved color (WI and YI); higher melt strength, and; improved heat sealing properties (e.g. heat sealing and hot tack).
These recited performance attributes are not to be construed as limiting. The polymerization process and catalyst formulations disclosed herein allow the production of ethylene interpolymer products that can be converted into flexible film articles that have a unique balance of physical properties (i.e. several end-use properties can be balanced (as desired) through multidimensional optimization); relative to comparative polyethylenes of comparable density and melt index.